Chop,

You cant really go wrong with the Canon and the 350d has a lot of features (more than my 20d probably ) The only complaint I hear about it is that it is too small and too light which can make it hard to take steady shots. I guess you can buy the battery grip to resolve this (a big chunky thing that its to the bottom of the camera and holds more battery power)

I would be weary of using a 1.4 or 2x converter etc on anything other than the fastest most expensive lenses. Using the convertors basically loses you a few F stops on the apperture. For most UK trackdays etc currently I am struggling using maximum apperture to let in enough light. Usin a convertor efectively blocks out the light and you may find you need to use a tripod everywhere.

Pop down to Jessops and get a hold for the cameras, then buy the one you like off the net. remember for most photographers, the body is the disposible part, it is the lenses that you keep for many many years!

Perosnally I don't think you could go far wrong if you stick to Canon or Nikon. These are what the pros use and what all the lenses and accessories are made for.

I would write more but it is 10 past midnight here and I have just done 3 12 hour days already so my brain is goosed